A PCI-to-PCI bridge chip has been proposed to extend the PCI bus in a personal computer. This chip provides a connection path between two independent PCI buses, and allows transactions to occur between a master on one PCI bus and a slave on the other PCI bus. This PCI-to-PCI bridge permits creation of hierarchical PCI buses in a computer, so as to overcome electrical and loading limits in the original PCI bus of a computer. Basically, a PCI-to-PCI bridge chip has a first interface for connection to a first PCI bus--e.g. a PCI bus connected to the host bridge of a host bus in a computer--and a second interface for connection to a second PCI bus. 25
FIG. 1 is a diagrammatic view of a configuration of a PCI-to-PCI bridge chip. The chip 1 comprises a primary interface 2 for connecting to a first PCI bus, a secondary interface 3 for connecting to a second PCI bus, a data path 4 between the primary and secondary interfaces, and a control path 5 between the primary and secondary interfaces. The control path 5 may for instance comprise a primary slave interface 6 and a primary master interface 8, both connected to the primary interface 2; a secondary master interface 7 and a secondary slave interface 9, both connected to the secondary interface 3. The primary slave interface 6 is also connected to the secondary master interface 7, and the primary master interface 8 is connected to the secondary slave interface 9. The primary slave interface 6 receives a transaction transmitted by a master on a PCI bus connected to the primary interface and passes it to the secondary master interface 7. It also controls the configuration of the data path 4. The secondary master interface 7 transmits the transaction to a slave located on a PCI bus connected to the secondary interface. A transaction from a master on a PCI bus connected to the secondary interface to a slave located on a PCI bus connected to the primary interface is handled similarly by the secondary slave interface 9 and the primary master interface 8.
This PCI-to-PCI bridge is satisfactory as a solution to the above mentioned problem of electrical loading. It is also satisfactory for providing exclusive PCI-to-PCI connection in a computer, that is for transmitting and receiving PCI transactions.